measurement and processing to determine land-mobile radio (lmr) channel occupancy

Measurement and Processing to Determine Land-mobile Radio (LMR)

Channel OccupancyRandy Hoffman

ISART 2005

Topics of DiscussionTopics of Discussion

Who are we?Who are we? Purpose of measurementsPurpose of measurements ChallengesChallenges Techniques for Techniques for

measurement measurement Post processing methodsPost processing methods

Radio Spectrum Measurement Radio Spectrum Measurement

Program - MissionProgram - Mission

To provide the Executive Branch, critically needed:

Radio spectrum data

Data analysis

Reports and summaries

SecretaryDeputy Secretary

Chief of Staff

Deputy Chief of Staff

Office of Public Affairs

Office of BusinessLiason

Office of Policyand Stragegic Planning

Office ofWhite House Liason

General Counsel

Inspector General

Chief Financial Officer andAssist Sec for Admin

Chief Information Officer

Under Secretaryand Administrator

National Oceanic andAtmospheric Admin

Under Secretary forInternational Trade

International TradeAdministration

Under Secretary forIndustry and Security

Bureau of Industryand Security

Under Secretary forEconomic Affairs

Economic andStatistics Admin

Under Secretary forTechnology

TechnologyAdministration

Under Secretary forIntellectual Property & Dir

U.S. Patent andTrademark Office

Assist Secfor Oceans &Atmosphere& DeputyAdmin

Assist Secfor MarketAccess &Compliance

Assist Secfor ImportAdmin

Assist Sec &Dir GeneralU.S. &Foreign

Comm Serv

Assist Secfor Trade

Development

Assist Secfor ExportAdmin

Assist Secfor ExportEnforcement

ChiefEconomist

DirectorBureau ofEconomicAnalysis

DirectorBureau ofthe Census

Assist Secfor

TechnonlogyPolicy

DirectorNational TechInformationServices

DirectorNational Instof Standards

andTechnology

Assistant Secretaryfor Economic Devel

Economic DevelAdministration

National Director

Minority BusinessDevelopment Agency

Assistant Secretary forCommunications and

InformationNat'l Telecommunications& Information Admin

U.S. Department of Commerce

National Telecommunications and Information Administration

NTIAOffice of the Assistant Secretary

Office of SpectrumManagement

Office of PolicyCoordination andManagement

Office ofInternational Affairs

Office ofCongressionalAffairs

Office of PublicAffairs

Office of Telecomand InformationApplications

Institude forTelecommunicationSciences

Office of PolicyAnalysis andDevelopment

Office of ChiefCounsel

ResponsibilitiesResponsibilities

Under Departmental Organization Order Under Departmental Organization Order 25-7, issued 5 October 1992, and 25-7, issued 5 October 1992, and amended 3 December 1993, the amended 3 December 1993, the NTIA NTIA Office of Spectrum Management (OSM) is Office of Spectrum Management (OSM) is responsible for identifying and making responsible for identifying and making arrangements for measurementsarrangements for measurements necessary to provide NTIA and the various necessary to provide NTIA and the various departments and agencies with departments and agencies with information information to ensure effective and to ensure effective and efficient use of the spectrum.efficient use of the spectrum.

The Radio Spectrum Measurement SystemThe Radio Spectrum Measurement System (RSMS) resides at ITS and is tasked to (RSMS) resides at ITS and is tasked to perform spectrum measurementsperform spectrum measurements as as required to fulfill this mission.required to fulfill this mission.

Why LMR Measurements?Why LMR Measurements?

Update Update usage trendusage trend information information comparing data collected in mid 70’s comparing data collected in mid 70’s – – for future LMR spectrum for future LMR spectrum managementmanagement..

To determine To determine current usage:current usage:– to help with decisions regarding how to to help with decisions regarding how to

makemake federal federal LMR radio operations LMR radio operations more efficientmore efficient..

– Provide information for realistic Provide information for realistic design design of possible shared trunked systemof possible shared trunked system..

ChallengesChallenges

Wide dynamic rangeWide dynamic range– Need for high sensitivity (low noise Need for high sensitivity (low noise

figure)figure)– Strong local signalsStrong local signals– 100 dB Dynamic Range100 dB Dynamic Range


Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing

– Need to resolve individual channels Need to resolve individual channels with a minimum of 12.5 kHz spacingwith a minimum of 12.5 kHz spacing

– Requires: Requires: narrow resolution bandwidthnarrow resolution bandwidth sharp roll-offsharp roll-off large stopband attenuation.large stopband attenuation.


Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise

– Need to know what is system noise Need to know what is system noise and what is signaland what is signal


Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise

– Need to reduce the probability that Need to reduce the probability that impulsive noise is mistaken for a impulsive noise is mistaken for a signalsignal


Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals

– System overloadSystem overload– Complicate in-band thresholdsComplicate in-band thresholds


Wide dynamic rangeWide dynamic range Narrow channel spacingNarrow channel spacing Differentiation from system noiseDifferentiation from system noise Impulsive noiseImpulsive noise Strong out-of-band signalsStrong out-of-band signals Strong in-band signalsStrong in-band signals

– System overloadSystem overload



– Intermodulation productsIntermodulation products

IM = +/- mF1 +/-nF2



– Sideband noiseSideband noise

Measurement SystemMeasurement System

Measurement ProcedureMeasurement Procedure Careful site selectionCareful site selection Signals detected by measuring RF energy at the Signals detected by measuring RF energy at the

channel frequency – channel frequency – inferring LMR transmissioninferring LMR transmission if if signal greater than system noise.signal greater than system noise.

Digitized at Digitized at 30 Msamples/s30 Msamples/s in 5.5 MHz bandwidth in 5.5 MHz bandwidth chunkschunks

Do Do fftfft with with flattop windowflattop window, , decimateddecimated to 12.5 kHz or to 12.5 kHz or 15 kHz spacing with samples centered on the 15 kHz spacing with samples centered on the channels, and channels, and downloaded via internetdownloaded via internet connection. connection.

Acquisition every Acquisition every 200 ms200 ms (up to (up to 480 channels480 channels) ) Capability for Capability for message length statisticsmessage length statistics.. Measure for Measure for 4 minutes / 5.5 MHz span4 minutes / 5.5 MHz span and switch to and switch to

next span. Sufficient data to characterize the next span. Sufficient data to characterize the channel every hour. Measure channel every hour. Measure 24 hours/day for a 24 hours/day for a weekweek..

Throw awayThrow away data during data during overloadoverload conditions conditions

Median ProcessingMedian Processing

Resolution BandwidthResolution Bandwidth

Post Processing – Post Processing – IntermodulationIntermodulation

Post Processing – Sideband Post Processing – Sideband NoiseNoise

Post Processing – Min Post Processing – Min ThresholdThreshold

Post Processing – Impulsive Post Processing – Impulsive NoiseNoise

SummarySummary Challenges and SolutionsChallenges and Solutions

– Wide Dynamic RangeWide Dynamic Range– Narrow Channel SpacingNarrow Channel Spacing– Differentiation from System NoiseDifferentiation from System Noise– Impulsive NoiseImpulsive Noise– Strong Out-of-band SignalsStrong Out-of-band Signals– Strong In-band SignalsStrong In-band Signals

OverloadOverload Intermodulation ProductsIntermodulation Products Sideband NoiseSideband Noise

Report – to be published this yearReport – to be published this year

measurement and processing to determine land-mobile radio (lmr) channel occupancy

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